Origin of the 0·5 eV infrared conductivity peak in YBa2Cu3O7-x

Abstract Two effects are invoked to account for the middle—infrared band observed in the optical conductivity of ceramics and sintered YBa2Cu3O7-x, the partial detection of the reflected light due to the granularity of the samples and the change of scattering regime when the wavelength is smaller or larger than the average grain size of the sample. We conclude that the analysis of infrared reflectance of ceramic powders or films should be more elaborate than what was the practice in earlier studies.